why not have all quests have a voice over?

[Bearded]

Voice acting takes time, translation and space on disks. Whilst it is true that some games are near enough 100% voice acted they limit themselves in that way in being able to deliver content simply because it will need to be voice acted, translated and so on. Plain text still needs to be translated but you do not then need to employ voice actors and studios to record it so content can be produced quicker.

Keep the voice acting to set parts I say and text for the rest so we can ensure content keeps on flowing.

[GrizzlyTank]

Voice acting takes time, translation and space on disks. Whilst it is true that some games are near enough 100% voice acted they limit themselves in that way in being able to deliver content simply because it will need to be voice acted, translated and so on. Plain text still needs to be translated but you do not then need to employ voice actors and studios to record it so content can be produced quicker.

Keep the voice acting to set parts I say and text for the rest so we can ensure content keeps on flowing.

Pretty much. Voice acting is also unfortunately one of the most storage demanding features a game can have.